1. Field of the Invention
The leveling of the surface of a paper strip, performed by means of a calendar, a smoothing machine, or a roller press can serve various purposes, such as the establishment of a certain thickness of the paper strip, compensation of thickness fluctuations to improve the winding process, or the compression of the paper strip to the point of transparency. In many cases, leveling is also important in order to increase the smoothness and the sheen of the surface of the strip, because the printability of a piece of paper depends upon the sheen and smoothness of its surface.
2. Description of the Prior Art
It is known that the pressure effective on the strip in the roller nip, the surface temperature of the rollers forming the roller nip, and the surface moisture of the strip effect the sheen and smoothness of a paper. Calendars are, therefore, as a general rule, especially equipped with a load device for adjusting the pressure effective on the strip in the roller nip, and are often also equipped with a heating and cooling device for the hard rollers or for at least some of the hard rollers. To increase the surface moisture of the paper strip, it is known to provide one or more vapor jet moisturizers on the calendar. These moisturizers can produce a film of moisture on the surface of the paper strip directly before it enters the roller nip.
In known devices for leveling the surface of a paper strip, the adjustment of the pressure and the roller nip and sometimes the roller temperature as well as the surface moisture of the strip for individual types of paper is performed by servicing personnel on the basis of their experience. If the load device, the temperature device, and the moisture device are in a regulating circuit, then the setting of the set point value is performed by the servicing personnel also on the basis of their experience. The results of the leveling process are thus dependent in both cases basically on the knowledge and care of the servicing personnel. This is unsatisfactory both because it is a source of mistakes and because of the dependency on the ability of the servicing personnel.